The present invention relates to a process for the growth of single crystals, and, in particular, a process for the growth of ZnGeP.sub.2 single crystals.
Several different growth techniques have been used by researchers to obtain single crystals of ZnGeP.sub.2. The equilibrium vapor pressure of phosphorous over ZnGeP.sub.2 at the 1025.degree. C. melting point is about 3.5 atm. The disordered .beta. phase is stable above 952 C., however the crystal structure of the high temperature phase has never been determined. Only the tetragonal .alpha. phase, stable below 952 C., has been identified.
A typical method for ZnGeP.sub.2 synthesis involves the high temperature reaction of small amounts of the elements Zn, Ge, and P in a sealed quartz ampoule. The high vapor pressure of phosphorous over the melt during the reaction process and the rupture strength of the quartz ampoule has limited the charge size in the past to about 40 g. An adequately sized crystal growth charge then requires the use of several presynthesized charges.